1. Field of the Invention
The present invention relates to the plugging of tapholes in furnaces such as, for example, blast furnaces employed in the production of steel. More specifically, this invention is directed to an improved apparatus for sealing the pouring holes of shaft furnaces. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in sealing the pouring holes of a shaft furnace. Such taphole plugging or sealing devices are known in the art as "clay guns." For a general discussion of the operation of clay guns, reference may be had to U.S. Pat. No. 3,765,663 which is assigned to the assignee of the present invention.
The tapholes of a shaft furnace are plugged by injecting thereinto, at very high pressure, a sealing compound which generally consists of clay. The clay injecting mechanism or clay gun is provided with a hydraulic jack which actuates an ejector piston. The clay ejector piston of the clay gun slides within a clay chamber and serves to remove material supplied to this chamber via a "nose" which is inserted into the furnace taphole. Modern blast furnaces operate at very high counter-pressures and thus, as noted above, the sealing compound must be ejected from the clay gun at a high pressure. The requisite high sealing compound ejection pressure can be obtained only by actuating the ejector piston of the clay gun by means of a hydraulic jack.
The loading of a clay gun typically comprises a plurality of repetitive steps wherein slugs or piles of sealing compound are delivered to the clay chamber through an aperture and individually moved forward to permit the delivery of additional material to the chamber. The sealing compound or clay is delivered to the clay chamber when the ejector piston is in the retracted position and when the clay gun is positioned in a substantially horizontal plane. The clay, because of its physical nature, has a tendency to accumulate beneath the loading aperture or port and obstructs this aperture. In order to clear the obstruction, and thus continue the chamber loading process, the ejector piston is operated to force the sealing compound towards the nose of the clay gun. After the ejector piston has been returned to its retracted position, further sealing compound can be introduced into the clay chamber and this operational sequence is repeated until the clay chamber has been filled.
During the clay gun loading operation, some of the taphole sealing compound may fall from the vicinity of the loading aperture into the clay chamber on the rod side of the ejector piston. This material will then be moved toward the rear of the clay chamber when the ejector piston is retracted. There will, additionally, be some leakage of sealing compound around the ejector piston. The sealing compound introduced into the clay gun contains abrasive particles which could easily damage the surface of the ejector piston rod, which is usually chromium, and which could also be transported on the rod into the hydraulic jack thereby scoring sealing surfaces. In order to prevent any appreciable quantity of taphole sealing compound, hereinafter called the "clay," from accumulating on the rod side or "upstream" of the ejector piston, frequent cleaning of the clay gun must be performed. This cleaning insures that the movements of the ejector piston will not be impeded and also prevents rapid wear of the piston rod and the sealing surfaces and packings of the hydraulic jack. Damage to the surface of the ejector piston rod or the sealing surfaces of the hydraulic jack would result in leakage of hydraulic fluid which must, to the extent possible, be avoided.
The cleaning of prior art clay guns, to remove material which gets behind the ejector piston, is a difficult task since the clay chamber at the rod side of the ejector piston is not readily accessible. The difficulty incident to the cleaning procedure is heightened because of the precautions which must be taken in order to assure that the piston rod will not be damaged by the cleaning tools.